In normal circumstances, this would be a very upbeat time for Just TV, the production company that makes Channel 4's Trial and Error programmes. Only 10 days ago, the subject of the very first Trial and Error investi gation, Mary Druhan, was freed after 10 years of wrongful imprisonment when the Lord Chief Justice quashed her conviction.

The company recently received the Royal Television Society's inaugural award for specialist journal ism; and, earlier this month, the value of this area of journalism was acknowledged at the highest levels of the judiciary.

In the past, some senior judges might have given the impression that they would like to see all investigative journalists put down, not necessarily humanely. Now, however, a more benign disposition was in evidence. The House of Lords bestowed belated recognition of some fine achievements: "It has been demonstrated that in recent years a substantial number of miscarriages of justice have only been identified and corrected as a result of painstaking investigation by journalists."

Lord Steyn quoted with approval the observations of the solicitor Gareth Peirce that television programmes frequently formed "the most significant chance of discovering new evidence".

So, in such an encouraging atmosphere, are they in party mood at Just TV? Not exactly - Channel 4 has just cancelled Trial and Error.

The official explanation is that the channel needs to keep reinventing itself, although some viewers may soon suspect that reinvention is merely a process of replacing outstanding programmes with mediocre ones.

In legal circles the news was received with despondency. "In many cases, lawyers and journalists have worked in partnership," said Campbell Malone, a solicitor and member of Just TV's advisory board. "The involvement of Trial and Error has given cases added weight and galvanised judicial channels. They've been an avenue of hope to those wrongly convicted."

Others are equally despairing. "It's obviously very disappointing," said Sir Ludovic Kennedy, the patron of Just TV. "On the other hand, I do understand it. Miscar riages of justice are now commonplace as far as the public is concerned. They don't have the shock of the new any more."

In the highly competitive arena of independent television production, Just TV - set up by Stephen Phelps, David Jessel and Stephen Haywood, all formerly from the BBC's Rough Justice programme - was placed outside the fray by Michael Grade, then chief executive of Channel 4. The company received ring-fenced annual funding to employ a small team of investigative journalists. As a result, it could guarantee that from the day a case was first brought to its attention, it would be examined by researchers with particular expertise in the sometimes arcane mechanics of the criminal justice system.

Then, at the other end of the legal process, Just TV would still be around, years after the trans mission of the programme, to liaise with lawyers and bodies like the Criminal Cases Review Commission in assisting the passage of a case up to the denouement at the appeal court. Out of 11 English cases screened by Trial and Error, four have been successful at appeal, three have been referred to appeal, and the other four are being considered by the CCRC.

There would also be an altruistic aspect to the research. "I know of dozens of cases that they've worked on where there was never any possibility of a programme," said Malone. "And they've been able to make progress in those." It must be emphasised, of course, that it is no responsibility of Channel 4's to fund the remedying of deficiencies in the criminal justice system.

In any event, Channel 4 has pledged to continue to commission investigations of this type, albeit for different strands. There is also the Rough Justice unit, which performs a parallel service at the BBC and which, presumably, can now expect to see its mailbag doubled.

What should give rise to concern is the rapid erosion of journalistic rigour and authority in television, something which the axing of Trial and Error does nothing to arrest. It should hardly be a surprise that there are continuing embarrassing revelations about the quality and integrity of some factual programmes when core units that could serve as models of excellence are being dismantled.

In such unpropitious times, that inaugural award for specialist journalism may well prove to be the last. In most areas of television journalism, investigative programmes are now either made by teams who have been parachuted in and can have little understanding of the background issues, or they are not made at all.

"The critical distinction," explained Jessel, the presenter of Trial and Error, "is between programmes which describe the def-ence and those which discover it."

The final irony about the end of Trial and Error is that it comes just as there is renewed concern about the level of miscarriages of justice. Last year was a vintage year, with the convictions of Sion Jenkins, Miles Evans, Helen Stacey and Michael Stone, among many others, creating fresh alarm.

"I'm very proud of our work," said Jessel. "Investigative journalism, to a standard where it is accep-ted by the Court of Appeal, is not the worst thing that television does."

 Trial and Error's examination of the Sion Jenkins case, originally scheduled for this evening, will now be transmitted in early autumn.